OBSERVATIONS:
- The power source used for the GTRM seems to make a significant difference. I’ve settled on USB battery packs which seem to output true DC and don’t interfere w/ the cutting/playback like wall adapters. Wall plug USB adapters seem to output pulsating DC and lots of audible hum.
- The consensus seems to be to use a cutter setting between .9cm and 1.1cm, and I typically cut on the deeper side, though I’m beginning to suspect the deep cut is degrading my fidelity.
- You MUST feed it mono. Even though the unit ships with a stereo-to-mono cable, my results are significantly better when my source is outputting true mono and not summing the signal at the destination. My SOP is to use a mid/side EQ and cut out all side signal, which allows me to drive the cutter harder and reduces vibration.
- Isolating the GTRM from the surface it sits on is also critical. Vibration ruins cuts, and the cutter head’s own vibrations will cause the chassis to resonate and the head will start jumping. I picked up some silicone hemispheres from Hudson Hi-fi which seem to help a lot with eliminating needle jumps.
- I lubricated the GTRM gears and cutter track with white lithium grease, and had very good results with that. It’s especially helpful with eliminating wobble in the cutter track.
- I’ve pretty much cracked being able to cut a full 4 minutes per side by using a second GTRM as an uptake reel for the swarf. I mount a cylinder of packing foam on the spindle wrapped with masking tape w/ adhesive side out. I grab the swarf under the cutter and lead it to the uptake reel. This method keeps the swarf away from the cutter and performs better than looping the swarf around the cutter’s spindle. I can cut 4 or 5 records before I need to clean the swarf off the cylinder.
- I’ve tried using lighter fluid on disks, and it does seem to show the gunk and help me clean the disk before a cut, but it leaves the PS looking really dull and I can’t really hear a difference from the cleaning, even when letting it soak for 5 minutes.
- I picked up some 5” BLANQ disks to try out, and learned the hard way these are only suitable for embossing w/ the Gakken. I probably ruined 2 needles trying to cut on these disks even with lighter fluid for lubrication. I watched Ethic Radio’s video on YouTube where they cut/emboss a BLANQ and I can’t even approximate the quality they achieved. I may build a dedicated GTRM embosser with a flipped needle to work on improving my cuts since they play so cleanly, but the output is very quiet and my test cuts track awful on a real turntable. I’d really like to get a working configuration with the BLANQs since they are CD-sized and there are more packaging options out there.
- I’ve also tried lubricating the surface of a PS disk with the white lithium, and it seems to help with surface noise and fidelity, but the record winds up pretty messy. I presume this is similar to lubricating with turtle wax--haven’t tried that yet.
- I have not heated any PS or PETG disks before cutting. LaserActiveGuy on YouTube mentions microwaving his disks, but I haven’t tried yet
- The cutter’s axle binds pretty badly, and the tension spring tends to bind if the adjustment screw is torqued down. Haven’t experimented with that yet, but will probably have to as I try cutting lighter.
- Integrated cartridges like Ortofon Concorde struggle to maintain tracking in the last ⅔ of a GTRM cut 5”. The needle will typically jump and run to center. I’ve got a ½ inch headshell with an AT needle mounted at an angle and wired mono (parallel) that will play a full 4 minute cut, but doesn’t sound that great.
- Is there a standard calibration procedure for setting up a new cutter? I started with pink noise and wound up down the rabbit hole trying to troubleshoot/overcome the sharp 5K drop-off the cutter has. I’ve tinkered with adding a severe boost at 5K+, and have managed to get the cutter to cut 8K, and even up to 10K at ghostly levels, but the bass is pretty much eliminated to drive the high-end hard enough. Seems like I’m fighting with the noise floor now.
- Has anyone ever posted audio files for calibrating a cutter head?
- Is there a method to identify optimal cut depth and cut volume? I can drive the head pretty hard from the headphone output of my Focusrite iTrack.
- Does the lighter fluid actually lubricate the cut, or only clean the surface?
- How do I know if static is an issue with my disks and cuts?
- Has anyone traced the circuit on the GTRM PCB? I’m wondering if the PCB has any internal EQing that accounts for the 5K roll off, or if it’s just the physical limitations of the needle and chassis.
- Are there any known sources for PS disks?
-Brian
